- Patients undergo leukapheresis or have several tubes of blood drawn from a vein to determine the effects of RFT-5-dgA on the immune system. This is done before the first dose of RFT-5-dgA, after the first three doses, and possibly during subsequent treatment courses in those patients who receive additional treatment. For leukapheresis, blood is collected through a needle in an arm vein and flows through a catheter into a machine that separates it into its components by spinning. The white cells are extracted and the rest of the blood is returned through another needle in the other arm.